1. Technical Field
The present invention relates to a glass base material elongating method.
2. Related Art
A glass base material for an optical fiber has its outer diameter and length adjusted by an elongating process using an elongation apparatus. As a result, the glass base material is formed to correspond to the specifications of the drawing equipment. Patent Document 1 describes a method for, when elongating a glass base material, determining the reference outer diameter position of the glass base material.    Patent Document 1: Japanese Patent No. 4443433
When elongating the glass base material, it is easy for outer diameter fluctuation, which is fluctuation in the outer diameter across the longitudinal direction, to occur during the initial portion of the elongating. In the portions where outer diameter fluctuation occurs, there is a decrease in the quality of the product, e.g. the optical fiber, obtained from the drawing. Therefore, the outer diameter fluctuation of the glass base material causes a drop in the yield.